60 Periorbital surgery Flashcards
Name the seven bones that make up the orbit.
Name the seven bones that make up the orbit.
Sphenoid, maxillary, ethmoid, lacrimal, zygoma, palantine, and frontal
What are the distances of the anterior ethmoid artery, posterior ethmoid artery, and optic canal from the orbital rim?
What are the distances of the anterior ethmoid artery, posterior ethmoid artery, and optic canal from the orbital rim?
This can be remembered by the mnemonic 24-12-6. The anterior ethmoid is approximately 24 mm from the orbital rim, the posterior ethmoid is another 12 mm posterior to that, and the optic canal is another 6 mm.
An object travels through the upper eyelid 12 mm superior to the lid margin. What structures does it travel through?
An object travels through the upper eyelid 12 mm superior to the lid margin. What structures does it travel through?
In the upper eyelid, the tarsus is typically not taller than 10 mm. So at 12 mm, the object will travel above the tarsus. The layers from anterior to posterior are the skin, orbicularis oculi, orbital septum, preaponeurotic fat, levator aponeurosis, Müller’s muscle, and conjunctiva.
What are the eyelid lamellae?
What are the eyelid lamellae?
The eyelid is sometimes conceptualized as consisting of an anterior and a posterior lamella. The anterior lamella consists of the skin, and the layer of striated muscle fibers of the orbicularis muscle. The posterior lamella consists of the tarsal plates, a layer of smooth muscle (Müller’s palpebral muscle), and the palpebral conjunctiva. The anterior and posterior lamellae are separated by the orbital septum.
What is the difference between dermatochalasis and blepharoptosis?
What is the difference between dermatochalasis and blepharoptosis?
Dermatochalasis refers to excess skin on the upper eyelid. When severe, it can hang down over the upper eyelid lashes and block the superior visual field. Blepharoptosis refers to drooping of the eyelid, often due to levator dysfunction.
How is dermatochalasis repaired?
How is dermatochalasis repaired?
By performing a blepharoplasty. In this procedure, excess skin, and occasionally orbicularis muscle, is excised. If there is excessive preaponeurotic or orbital fat, it can be judiciously excised by opening the septum.
How is blepharoptosis repaired?
How is blepharoptosis repaired?
The two most common methods to repair blepharoptosis are external levator advancement (ELA) and Müller’s muscle conjunctiva resection (MMCR). ELA involves a skin incision at the lid crease, whereas MMCR is performed on the conjunctival side of the upper lid. When levator function is poor, such as in congenital ptosis, the upper eyelid can be tethered to the frontalis muscle to assist in eyelid elevation. This is known as a frontalis sling.
The contralateral eyelid occasionally falls after ipsilateral blepharoptosis repair. Why does this happen?
The contralateral eyelid occasionally falls after ipsilateral blepharoptosis repair. Why does this happen?
Hering’s law of equal innervation postulates that yoke muscles receive equal innervation. More specifically, when one eyelid is ptotic, the brain increases innervation to both levator palpebrae muscles in an attempt to clear the visual axis. The increased innervation to the contralateral eyelid can result in pseudoretraction. After repair of unilateral blepharoptosis, the innervation to the levator palpebrae is decreased and a drop of the contralateral eyelid may occur.
What is the best treatment a patient with biopsy-proven basal cell carcinoma of the lower eyelid?
What is the best treatment a patient with biopsy-proven basal cell carcinoma of the lower eyelid?
Complete excision with frozen sections. Alternatively, they can be referred to a Mohs surgeon for excision.
What principles should be kept in mind when planning reconstruction of an eyelid defect?
What principles should be kept in mind when planning reconstruction of an eyelid defect?
Important principles include avoiding vertical tension and maintaining a good vascular supply. Minimizing vertical tension avoids eyelid retraction. When a full thickness defect is present, only one lamella can be repaired with a free graft. If both anterior and posterior lamella are replaced with free grafts, the rate of failure is high due to lack of blood supply.
What is ectropion? What are the causes?
What is ectropion? What are the causes?
Ectropion is outward turning of the eyelid. Causes can be involutional, paralytic, mechanical, cicatricial, and congenital in nature.
What is entropion? What are the causes?
What is entropion? What are the causes?
Entropion is an inward turning of the eyelid. Causes can be involutional, acute spastic, cicatricial, and congenital in nature.
How does repair of involutional ectropion and entropion differ?
How does repair of involutional ectropion and entropion differ?
Both involve horizontal shortening of the eyelid. For ectropion, this is usually sufficient. For entropion, the surgeon must also reattach the lower lid retractors to the tarsus to avoid recurrence.
If a patient with thyroid eye disease has proptosis, strabismus, and eyelid retraction, what is the order of surgeries to correct their issues?
If a patient with thyroid eye disease has proptosis, strabismus, and eyelid retraction, what is the order of surgeries to correct their issues?
They should first have a decompression, followed by strabismus surgery, then correction of eyelid retraction. This is because decompression can alter strabismus, and strabismus surgery can alter eyelid position.
Name five surgical incisions to approach the orbit.
Name five surgical incisions to approach the orbit.
Transconjunctival, lateral canthotomy, upper lid skin crease, transcaruncular, vertical lid split.
